BAGHDAD 
Iraq's parliament speaker warned Thursday that the escape this week of hundreds of inmates during al-Qaida-claimed raids on prisons outside Baghdad will make the country's rapidly deteriorating security even worse.

The warning came just hours after militants carried out a bold ambush on truckers north of the capital, killing 14 people.

The Sunday night attack on the notorious Abu Ghraib prison and another lock-up in Taji, both on the outskirts of Baghdad, underscored the extent of the challenges facing Iraqi authorities as they struggle to keep the country safe. More than 550 people have been killed in violent attacks so far this month.

Dozens of people, mainly members of the security forces and inmates, were killed in the attacks. Iraqi officials have yet to release a comprehensive account of the raids, but there is little dispute that several hundred inmates, including members of al-Qaida, escaped.

At a press conference Thursday in Baghdad, the parliament speaker, Osama al-Nujaifi, said the latest reports indicate that more than 500 prisoners escaped - a figure similar to what other Iraqi officials have provided - and noted that a parliamentary committee is investigating what happened.

"The situation is grave," said al-Nujaifi, a Sunni who has frequently criticized the Shiite prime minister, Nouri al-Maliki. "We don't know who they are and how dangerous they are, but this situation will be reflected negatively on the security situation."

Al-Qaida's Iraq branch claimed responsibility for the prison attacks Tuesday. Interpol issued its security alert Wednesday to warn counties in the region about the fugitives, calling the breakouts "a major threat to global security."

Many of the escaped prisoners were senior members of al-Qaida in Iraq, including some who were facing the death penalty, according to Interpol.

A new ambush targeting Shiites in northern Iraq highlighted the spiraling deterioration of security in the country.

Insurgents outside the village of Sarha launched mortar rounds at a nearby military base and bombed a communication tower to distract security forces. Then they quickly set up a fake checkpoint on a nearby highway to stop passing vehicles, said Col. Hussein Ali Rasheed, the police chief in nearby Tuz Khormato, about 200 kilometers (125 miles) north of Baghdad.

The corpses of 14 drivers and passengers in a convoy of trucks caught at the checkpoint, all of them Shiites, were later found, each killed by gunshot wounds to the head, Rasheed said.

In the northern city of Beiji, 250 kilometers (155 miles) north of Baghdad, militants shot and killed three off-duty soldiers as they were leaving a restaurant, provincial health official Raed Ibrahim said. The soldiers were on their way to Baghdad from Mosul.

And in the city of Kirkuk, a parked car bomb targeted a passing police patrol on Thursday morning, critically wounding six policemen, police Col. Salah Abdul-Qadir said. Kirkuk is 290 kilometers (180 miles) north of Baghdad.

Also, police said gunmen using pistols fitted with silencers shot and killed four people, including two street cleaners, in three separate incidents in Baghdad.

Thursday night, a bomb exploded during a small wedding party held in a house in Baghdad's Amiriyah neighborhood, killing three people and wounding 16 others, including some women and children, police and hospital officials said. The officials spoke on condition of anonymity as they were not authorized to speak to journalists.

Insurgents in recent months have ramped up attacks on civilians and government forces throughout Iraq.

The violence has reached levels not seen since 2008, fueling worries of a return to the widespread sectarian killing that pushed the country to the brink of civil war after the 2003 U.S.-led invasion. More than 3,000 people have been killed since April.